Osteoarthritis is the most common form of arthritis, affecting the hands, knees, hips, spine and other joints. Characteristics of osteoarthritis include a loss of cartilage, seen as a reduction in the joint space, and osteophytes (or bone spurs).
Arthritic pain is a leading cause of lost productivity. The cause of arthritic pain is unclear. The amount of cartilage loss correlates poorly with the severity of pain in an afflicted individual. Likewise, radiographic finding such as osteophytes (bone spurs) and thickening of subchondral bone (eburination) do not correlate with the presence or severity of pain.
Bone marrow lesions (or edemas) are very strongly associated with knee arthritis pain (Felson et al., “The association of bone marrow lesions with pain in knee osteoarthritis.” Ann Intern Med. 2001 Apr. 3; 134(7):541-9) and disease progression (Felson et al., “Bone marrow edema and its relation to progression of knee osteoarthritis.” Ann Intern Med. 2003 Sep. 2; 139(5 Pt 1):330-6). See also U.S. Pat. No. 6,564,083 to Stevens, which describes a method of identifying in a patient having joint pain the susceptibility of the patient to developing progressive osteoarthritis or loss of joint space, by determining the presence or absence of bone marrow edema about or of the joint. The determination is preferably made through the use of Magnetic Resonance Imaging (MRI).
The nature and cause of bone marrow lesions is poorly understood. Histologic examination of these lesions demonstrates abnormal bone with areas of fibrosis, osteonecrosis and extensive bone remodeling (Zanetti et al., “Bone Marrow Edema Pattern in Osteoarthritic Knees: Correlation between MR Imaging and Histologic Findings.” Radiology. 2000; 215:835-840). It has been suggested that they are related to inflammation (Bollet, “Edema of the bone marrow can cause pain in osteoarthritis and other diseases of bone and joints.” Ann Intern Med. 2001 Apr. 3; 134(7):591-3), venous hypertension (Arnoldi et al., “Intraosseous phlebography, intraosseous pressure measurements and 99mTc-polyphosphate scintigraphy in patients with various painful conditions in the hip and knee.” Acta Orthrop Scand. 1980; 51:19-28), or impaired arterial blood flow (McAlindon et al., “Magnetic resonance imaging in osteoarthritis of the knee: correlation with radiographic and scintigraphic findings.” Ann Rheum. Dis. 1991; 50:14-9. Others have suggested these lesions reflect increased bone stress and microfracture of the bone (see Felson et al. 2003, supra).
Knee arthritis affects millions of people and the pain associated with this disease can be disabling. Patients who initially present with painful knee arthritis are usually treated non-surgically. Non-surgical treatments are modestly effective at temporarily relieving pain, but not risk free. Pharmacologic intervention (i.e., non-steroidal anti-inflammatory drugs) has been reported to be associated with significant complications, such as gastric ulcers, strokes and heart attacks. Steroid or viscosupplement injection may lead to infection. Steroid injections may also have systemic effects such as increased blood sugar and hypertension. Generally speaking non-surgical interventions are most efficacious for early arthritic disease and do not prevent disease progression.
When patients fail non-surgical treatment, surgical intervention is often recommended. Arthroscopic surgery has been shown to have limited effectiveness and has a small role in the management of knee arthritis. More invasive surgical approaches such as high tibial osteotomy and partial or complete knee replacement predictably relieve pain. However, these major operations are also potentially associated with significant morbidity and occasional mortality. These risks along with the limited durability of implantable devices influence patient and physicians to defer surgery until the symptoms become unbearable.
Accordingly, it is desired to provide an effective, surgical treatment of osteoarthritis, and particularly knee arthritis pain. It is further desired that such surgical treatment be less invasive than high tibial osteotomy and partial or complete knee replacement.
All references cited herein are incorporated herein by reference in their entireties.